Historical Painting Techniques, Materials, and Studio Practice

2

Fortunately, the spirit of the eighteenth century in Britain fired a great en­

thusiasm fo r publications on technical matters, including the materials and

techniques of oil painting. Thus, we find a rich source of information in the

various treatises, manuals, and handbooks that continued to be published into

the nineteenth century. The fo llowing will be a discussion of the kind of

information these documentary sources can provide and how this information

can influence our interpretation of cross sections and analytical results as well

as fu rther our understanding of painters' techniques.

The painter's environment

The anonymous eighteenth-century author quoted previously placed great

fa ith in "facts judiciously arranged, and published from time to time as they

accumulate." Yet, however important a discrete piece of information, such as

the date of introduction of a new pigment, may be in the study of painters'

instruction books, it is not always this information that provides insight into

the painter's choice of materials. Sometimes it is the tangential information

about the experience of living at a given time that provides a context fo r

what we observe now.

In cross sections of paint, the build-up of dirt between layers of paint must

be interpreted in relation to past conditions fo r lighting and heating. We

cannot, based on our present-day experience, extrapolate from the thickness

of a dirt layer the length of time between episodes of painting. Here, those

who study the history of technology and of domestic life are of great help.

In one source on the history of domestic environments, we find that even as

early as 1700 the use of coal fo r heating in London resulted in a "Tartanous

Smoak" that sullied the environment both indoors and out: "All sorts of

Hangings, especially the Tapestry, are in a few Ye ars totally defil'd by it ... " (4).

Because painters who fo llowed the technique of "painting in stages" were

obliged to wait between applications of paint fo r the underlayers to dry, a

fa irly rapid build-up of dirt could be expected under the conditions described,

fa r more than our late twentieth-century environments would convey.

The level of air pollution in the days of coal heating also caused great concern

among artists and their chemist advisors with regard to the role of lead in

paintings. It was thought that the high levels of sulfur in the air caused re­

actions with lead-white pigment and with lead-treated oil, resulting in an

overall darkening of these materials due to the reaction product, lead sulfide.

Various solutions to this problem, including the application of nonreactive

zinc white over lead-white underlayers, were recommended. This advice to

apply zinc white over lead white was given not only fo r paint layers, but fo r

grounds as well; it was believed that a lead-white ground preparation could

also be subject to darkening. Cross sections taken from a painting in which

this advice had been fo llowed show layers of two different white paints, the

presence of which would not be immediately obvious without the knowledge

of the remedial steps taken to obviate the so-called lead-sulfide darkening (5).

Aside from the dirt and soot from coal heat and tallow candles, interior

environments were also substantially colder in the winter months. In the

absence of central heating, painters fo und that their colors dried significantly

more slowly during the winter months, hence the advice to add materials

that hasten drying at this time of year (see below).

Beliefs influencing artists' practices

Artists' practices were also influenced by views and beliefs that are fo reign to

our era. Conservators have discovered empirically that it was not uncommon

fo r nineteenth-century painters to use similar varnishes in the paint medium

to those used as a final varnish. In the literature, painters were quite explicit;

they believed that using the same resin in the medium as in the final varnish

would, by ensuring homogeneity of materials, reduce the likelihood of crack­

ing (6). In a pharmaceutical dictionary and recipe book published in 1764,

Historical Painting Techniques, Materials, and Studio Practice